This invention relates to a network device and a network system, which realize a live migration process to a different computer between locations.
In recent years, in order to effectively utilize hardware resources of a server, a virtual machine technology for virtualizing hardware installed in the server and for operating a plurality of operating systems (OSs) by using the virtualized hardware has been put into practical use. In the virtual machine technology, computing resources, memory resources, and input/output (I/O) resources need to be managed and scheduled. A control program therefor is called hypervisor.
One of known functions of the hypervisor is live migration. The live migration may be used to migrate a virtual machine between servers without any interruption. This makes it possible to realize load balancing, aggregation of hardware resources, and server maintenance across the system without service suspension.
In order to realize the live migration, it is a precondition that a storage area can be shared by the migration source server and the migration destination server. This is because in the live migration, information on a virtual memory used by the virtual machine and register information are migrated but a storage area having a large capacity is not migrated. Therefore, it has been difficult to realize the live migration between the servers located in physically distant locations due to the precondition.
In order to solve the above-mentioned problem, it is conceivable to couple the locations by means of a dedicated high-speed line and synchronize the storage area of the migration source and the storage area of the migration destination. However, in this method, there is a need to secure a storage area in the location of the migration source and the location of the migration destination at all times. The method also has a disadvantage in that a load is always imposed on a network band between the locations, which results in an increased operation cost.
As a method for solving the above-mentioned problem, there is known a method described in US 2009/0037680, for example. In the method described in US 2009/0037680, means for migrating a storage area used by the virtual machine without any interruption is realized by the hypervisor. Specifically, after migrating data stored in the storage area in preprocessing of the live migration, the hypervisor executes the live migration, to thereby realize the migration without any interruption of the virtual machine between the locations.